#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int febo(int a[100],int c)
{
	a[0] = 1; a[1] = 1;
	int i = 2;
	for (i = 2; i < c; i++)
	{
		a[i] = a[i - 1] + a[i - 2];
	}
	printf("%d", a[c-1]);
}
int main()
{
	int a[100] = { 0 }; int b = 0;
	scanf("%d", &b);
	febo(a,b);
}